This invention relates to novel nucleoside analogs, processes for their synthesis and incorporation into polynucleotides.
The following is a brief description of nucleoside analogs. This summary is not meant to be complete but is provided only for an understanding of the invention that follows. This summary is not an admission that all of the work described below is prior art to the claimed invention.
Nucleoside modifications of bases and sugars, have been discovered in a variety of naturally occurring RNA (e.g., tRNA, mRNA, rRNA; reviewed by Hall, 1971 The Modified Nucleosides in Nucleic Acids, Columbia University Press, New York; Limbach et al., 1994 Nucleic Acids Res. 22, 2183). In an attempt to understand the biological significance, structural and thermodynamic properties, and nuclease resistance of these nucleoside modifications in nucleic acids, several investigators have chemically synthesized nucleosides, nucleotides and phosphoramidites with various base and sugar modifications and incorporated them into oligonucleotides.
Uhlmann and Peyman, 1990, Chem. Reviews 90, 543, review the use of nucleoside modifications to stabilize antisense oligonucleotides.
Usman et al., International PCT Publication Nos. WO/93/15187; and WO 95/13378; describe the use of sugar, base and backbone modifications to enhance the nuclease stability of enzymatic nucleic acid molecules.
Eckstein et al., International PCT Publication No. WO 92/07065 describe the use of sugar, base and backbone modifications to enhance the nuclease stability of enzymatic nucleic acid molecules.
Grasby et al., 1994, Proc. Indian Acad. Sci., 106, 1003, review the "applications of synthetic oligoribonucleotide analogues in studies of RNA structure and function".
Eaton and Pieken, 1995, Annu. Rev. Biochem., 64, 837, review sugar, base and backbone modifications that enhance the nuclease stability of RNA molecules.
Hildbrand and Leumann, 1996, Agnew. Chem. Int. Ed. Engl., 35, 1968, describe a method for the synthesis of a 2-aminopyridine nucleoside derivative.
The references cited above are distinct from the presently claimed invention since they do not disclose and/or contemplate the synthesis of the nucleoside analogs of the instant invention.